The requirement of polyamines for neoplastic growth makes the polyamine metabolic pathway an attractive target for anti-neoplastic intervention. Recent advances in the design and testing of a new generation of polyamine analogues has improved the likelihood of discovering a breast tumor specific agent. In normal tissues, perturbations of polyamine metabolism generally leads to a decrease in growth rate but does not produce toxicity. However, through the use of the novel anti-neoplastic polyamine analogues instances of phenotype-specific cytotoxicity have been discovered in breast and other important human solid tumors. Although many new analogues have been synthesized, little work has been performed in the breast cancer systems. However, it was the breast cancer systems that first provided definitive evidence that the polyamine analogues killed cells through an induction of a programmed cell death pathway. Further, the induction of programmed cell death was found to result from both caspase dependent and-independent pathways. A series of preliminary studies in breast cancer cell lines has demonstrated that many unsymmetrically substituted polyamine analogues are highly effective in growth inhibiting or killing breast tumor lines regardless of their estrogen receptor status or their resistance to other chemotherapeutic agents, including adriamycin. The studies detailed in the current proposal are designed to expand upon the above and other findings with the polyamine analogues and to continue to design and synthesize additionally and potentially more efficacious anti-tumor agents. We will expand upon the finding that in some tumor systems the production of H2O2 as a by product of analogue induced polyamine catabolism is partly responsible for tumor specific toxicity. Our recent discovery that some polyamine analogues induce a profound G2/M block resultant from interference with tubulin polymerization will be examined to determine what role this mechanism may play in those breast cancer that are sensitive to the polyamine analogues. Based on the novel activities of the polyamine analogues, combinations of classical anti-proliferative agents with the new polyamine analogues will be examined for enhanced activity against a series of representative breast cancer lines with the goal of finding combinations which have significant clinical potential. Finally, when a sufficient number of analogous have been synthesized and tested, a systematic structure activity analysis will be performed to aid in the design of additional agents with the goal of improving upon effectiveness and selectivity against breast cancer. Finally, in collaboration with other members of this SPORE application, the possibility of combining the polyamine analogues with other modalities of breast cancer treatment, including immune modulation will be examined.